Manchester City were interested in taking Van Persie to the Etihad Stadium but, for the first time since Dimitar Berbatov preferred the red half of Manchester in 2008, they have missed out on a player to their rivals.

However, Mancini has said a deal to take Van Persie to City would not have been possible, given that his quartet of forwards - Sergio Aguero, Edin Dzeko, Mario Balotelli and Carlos Tevez - all remain at the club.

"We have four strikers," Mancini said. "It was impossible for us to put in another striker."

Mancini had already argued that United were the team to beat in the title race but believes the combination of Van Persie and Wayne Rooney, the division's two top scorers last season, cements that.

"United play for the title every year for 20 years," he said. "We won the last championship but we can't change this in one year. For this reason, they are favourites for the title and now with Van Persie... he is a really top player and was the best striker last year. With Rooney they will be one of the best couple of strikers in the Premier League.

"I think a fit Van Persie is one of the best strikers in the world. If they bought him because they need another striker, I am sure that now they are better with Van Persie."